xStack DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual
47
Figure 6- 22. STP Bridge Global Settings window - MSTP
NOTE:
The Hello Time cannot be longer than the Max. Age. Otherwise, a configuration error will
occur. Observe the following formulas when setting the above parameters:
Max. Age
≤
2 x (Forward Delay - 1 second)
Max. Age
≥
2 x (Hello Time + 1 second)
The following parameters can be set:
Parameter Description
STP Status
Use the pull-down menu to enable or disable STP globally on the Switch. The default is
Disabled
.
STP Version
Use the pull-down menu to choose the desired version of STP to be implemented on the Switch.
There are three choices:
STP
- Select this parameter to set the Spanning Tree Protocol (STP) globally on the switch.
RSTP
- Select this parameter to set the Rapid Spanning Tree Protocol (RSTP) globally on the
Switch.
MSTP
- Select this parameter to set the Multiple Spanning Tree Protocol (MSTP) globally on the
Switch.
Hello Time
The Hello Time can be set from
1
to
10
seconds. This is the interval between two transmissions
of BPDU packets sent by the Root Bridge to tell all other switches that it is indeed the Root
Bridge. This field will only appear here when STP or RSTP is selected for the STP Version. For
MSTP, the Hello Time must be set on a port per port basis. See the MST Port Settings section
for further details.
Max Age
The Max Age may be set to ensure that old information does not endlessly circulate through
redundant paths in the network, preventing the effective propagation of the new information. Set
by the Root Bridge, this value will aid in determining that the Switch has spanning tree
configuration values consistent with other devices on the bridged LAN. If the value ages out and
a BPDU has still not been received from the Root Bridge, the Switch will start sending its own
BPDU to all other switches for permission to become the Root Bridge. If it turns out that your
switch has the lowest Bridge Identifier, it will become the Root Bridge. The user may choose a
time between
6
and
40
seconds. The default value is
20
.
Forward Delay
The Forward Delay
can be from
4
to
30
seconds. Any port on the Switch spends this time in the
listening state while moving from the blocking state to the forwarding state.
Max Hops
Used to set the number of hops between devices in a spanning tree region before the BPDU
(bridge protocol data unit) packet sent by the Switch will be discarded. Each switch on the hop
count will reduce the hop count by one until the value reaches zero. The Switch will then discard
the BPDU packet and the information held for the port will age out. The user may set a hop count
from
1
to
20
. The default is
20
.
